For people that don't understand what work needs to be done at home, here are some examples for primary:
We plan our own lessons. There isn't some central place we can just download them all from. We have to think of learning objectives, teaching ideas and ideas for activities that include challenge for the more able and different activities for those who won't be able to do the standard work. We have to type up each of these plans - so five maths lessons, five English lessons and then usually around 10 afternoon lessons per week. Quite often, the children's learning goes in a different direction so you have to adjust your planning and rewrite it.
Each lesson needs resources. Most primary schools don't have textbooks so you make or source your own resources, eg PowerPoints, worksheets, writing frames, sentence starters etc. You need different resources for the children with SEN. Sometimes you can find some online but you still need to spend time searching and then adapting for your class.
After the work is done, it needs marking. Up to 30 lessons a week. Sometimes you can just tick but generally you have to make corrections, write comments, give children a "next step" or something to do to show they've understood. If it was a practical lesson, photos need sticking in. Everything needs to be evidenced.
If you work in an office-based job, imagine you had to prepare four presentations a day with activities for all participants then you had to give them all individual feedback.
That is it from a purely teaching point of view, but on top of that is record keeping, preparing assemblies and plays, clubs, creating displays etc.
It's not the most stressful in the world, although stress levels can vary depending on the demands of your SLT. But it is very time-consuming and tiring. Just managing 30 7-year olds for 6 hours a day is tiring, let alone all the preparation and work that goes into teaching them.